Management Fusarium Wilt of Sweet Pepper by Bacillus Strains

Abstract

Isolation trials from the roots of wilted sweet pepper plants yielded Alternaria spp., Fusarium oxysporum, Pythium spp., Rhizontonia solani , Sclerotium rolfsii and Trichoderma spp. The isolates of the fungus F. oxysporum were selected to test their pathogenicity and Kalubia isolate was the most virulent one. The fungus was virulent to sweet pepper and low infection was found in case of the other five tested plants. Therefore, the fungus F. oxysporum named Fusarium oxysporum f.sp. capsici. All the five Bacillus strains, i.e. Bacillus chitinosporus ,B. coagulans , B. humilus ,B.subtilis and B. thuringiensis caused significant reduction to the radial growth of F.o.f.sp.capsici compared with control treatment. In addition, the growth of the tested pathogen was completely inhibited by B.subtilis and B.thuringiensis at the concentration of 60%. Furthermore, B.thuringiensis was the most efficient bioagent in this regard followed by B.subtilis then B.pumilus. Adding the three tested bioagents ,i.e.B.pumilus .B.subtilis and B. Thuringiensis to soil infested with F.o.f.sp.capsici resulted in significant reduction to sweet pepper wilt with significant increase to the plant height as well as the number of pods and their weight / plant compared with control treatment. The symptoms of the disease were obvious both on the foliage growth and the xylem vesicles, but the severity of the disease was more higher on the xylem vesicles than on the foliage growth. In addition, plants grown in soil infested with Bacillus strains were of high values of plant height and fruit yield (number and weight / plant) than that grown in the control (uninfested soil). The total phenolic compounds were greatly increased in the bacterial treated plants as compared to untreated plants with the bioagents and that infested with the pathogen only. These results give a potential of these bacterial strains for use as plant protection agents against Fusarium wilt of sweet pepper. This work was performed to investigate the potential of some bacterial bioagents ,i.e. B. humilus , B.subtilis and B. thuringiensis on management of sweet pepper Fusarium wilt and the formation of phenolic compounds in the plants.